Model predictive strip position controller

1. An operating method for a roll train, in which a metal strip is rolled, wherein the roll train comprises at least one roll stand and a device disposed downstream of the roll stand; the method comprising: running the strip head out of the roll stand, and when running the strip head out of the roll stand, capturing a lateral position of the strip head by using a capture device at at least one location lying between the roll stand and the device disposed downstream; operating a strip position controller embodied as a model predictive controller; based on the captured lateral position of the strip head, establishing a sequence of control commands to be output in succession with a work cycle in order to laterally position the strip head by setting the roll gap wedge of the roll stand; wherein the number of control commands in conjunction with the work cycle defines a prediction horizon of the strip position controller; and applying the at least next control command of the strip position controller within the prediction horizon to the roll stand to set the roll gap wedge below a maximum roll gap wedge in order to laterally position the metal strip so that a lateral position of the strip does not exceed a maximum deviation from a set point position.

2. The operating method as claimed in claim 1 , further comprising: for the purpose of establishing the sequence of control commands to be output, operating the strip position controller to: initially formulate a sequence of preliminary control commands, and setting by means of which a roll gap wedge in each case by the preliminary control commands; establishing, in each case, the distance of the strip head from the roll stand which is to be expected when carrying out the formulated control commands up to a respectively considered control command; establishing the lateral position of the strip head which is to be expected when carrying out the formulated control commands up to a respectively considered control command for the formulated control commands based on a model of the roll train when proceeding from the captured lateral position of the strip head; and optimizing the formulated control commands according to an optimization criterion and thus establishing the control commands to be output.

3. The operating method as claimed in claim 2 , further comprising, establishing the control commands using the strip position controller such that, within the prediction horizon, a quality function is minimized; and the quality function including at least one of a respective change of the roll gap wedge for successive control commands and a penalty term comprising penalizing a predetermined maximum change of the roll gap wedge being exceeded for respective control commands.

4. The operating method as claimed in claim 3 , further comprising, when establishing the control commands, the strip position controller takes account of the deviation of the lateral position of the strip head from the setpoint position lying within an admissible end deviation at the end of the prediction horizon as an additional boundary condition.

5. The operating method as claimed in claim 3 , when establishing the control commands, the strip position controller takes account of a change in the lateral position of the strip head lying within an admissible end change at the end of the prediction horizon as an additional boundary condition.

6. The operating method as claimed in claim 1 , further comprising successively applying to the roll stand with the work cycle the further control commands to be output by using the strip position controller, and so applying either until all control commands to be output have been output or until the strip position controller establishes a sequence of control commands again based on a renewed capture of the lateral position of the strip head.

7. The operating method as claimed in claim 1 , further comprising the prediction horizon extends up to conveying the strip head to the downstream device.

8. The operating method as claimed in claim 1 , further comprising carrying out the method repeatedly while the strip head runs out of the roll stand so that only the most recently established control commands are valid.

9. The operating method as claimed in claim 1 , further comprising: applying the at least next control command of the strip position controller to the roll stand in order to set the position of the metal strip.

11. The operating method as claimed in claim 10 , further comprising: after applying a number of control commands to the roll stand capturing the lateral position of the strip head anew the curvature of the metal strip is caused by the metal strip and by the effectiveness of the control commands which are applied to the roll stand; and tracking the foregoing based on a comparison of the newly captured lateral position of the strip head with an expected lateral position of the strip head, wherein the expected lateral position of the strip head is the position that is expected within the scope of establishing the control commands after the control command that is last applied to the roll stand.

12. The operating method as claimed in claim 11 , further comprising the strip position controller uses a Kalman filter to track the curvature of the metal strip caused by the metal strip and tracks the effectiveness of the control commands that are applied to the roll stand.

13. The operating method as claimed in claim 10 , wherein the strip position controller initially establishes the effectiveness (λ 1 ) of the respective control command based on the relationship λ ⁢ ⁢ 1 = 2 L · ( s ⁢ ⁢ 1 + s ⁢ ⁢ 2 ) ( 3 ) or by way of the relationship λ ⁢ ⁢ 1 = 2 L · ( h ⁢ ⁢ 1 + h ⁢ ⁢ 2 ) ( 4 ) or by way of the relationship λ ⁢ ⁢ 1 = v ′ η 2 · d · v , ( 5 ) where L is a distance from an operating-side adjustment device for setting the roll gap of the roll stand to a drive-side adjustment device for setting the roll gap of the roll stand; s 1 and s 2 are an operating-side and a drive-side roll gap, h 1 and h 2 are an operating-side and a drive-side thickness of the metal strip; v′ is a speed of the metal strip on the intake side of the roll stand; η is a draft occurring when rolling the metal strip in the roll stand; and d is a thickness of the metal strip on the intake side of the roll stand.

14. A computer program having a non-transitory recording medium and comprising a machine code, the code can be executed by a control device for a roll train in which a metal strip is rolled, wherein the roll train comprises at least one roll stand and a device disposed downstream of the roll stand, wherein the executing of the machine code by the control device causes the control device to operate the roll train according to an operating method, the operating method comprising: running the strip head out of the roll stand, and when running the strip head out of the roll stand, capturing a lateral position of the strip head by using a capture device at at least one location lying between the roll stand and the device disposed downstream; operating a strip position controller embodied as a model predictive controller; based on the captured lateral position of the strip head, establishing a sequence of control commands to be output in succession with a work cycle in order to laterally position the strip head by setting the roll gap wedge of the roll stand; wherein the number of control commands in conjunction with the work cycle defines a prediction horizon of the strip position controller; and applying the at least next control command of the strip position controller within the prediction horizon to the roll stand to set the roll gap wedge below a maximum roll gap wedge in order to laterally position the metal strip so that a lateral position of the strip does not exceed a maximum deviation from a set point position.

15. A roll train for rolling a metal strip, wherein the roll train has at least one roll stand and a device disposed downstream of the roll stand along a path of the metal strip; and the roll train has a control device which operates the roll train according to an operating method, the operating method comprising: running the strip head out of the roll stand, and when running the strip head out of the roll stand, capturing a lateral position of the strip head by using a capture device at at least one location lying between the roll stand and the device disposed downstream; operating a strip position controller embodied as a model predictive controller; based on the captured lateral position of the strip head, establishing a sequence of control commands to be output in succession with a work cycle in order to laterally position the strip head by setting the roll gap wedge of the roll stand; wherein the number of control commands in conjunction with the work cycle defines a prediction horizon of the strip position controller; and applying the at least next control command of the strip position controller within the prediction horizon to the roll stand to set the roll gap wedge below a maximum roll gap wedge in order to laterally position the metal strip so that a lateral position of the strip does not exceed a maximum deviation from a set point position.